( 2010 )
Characterization of a novel Lactobacillus species closely related to Lactobacillus johnsonii using a combination of molecular and comparative genomics methods.
PMID : 20849602 : DOI : 10.1186/1471-2164-11-504 PMC : PMC2997000
Comparative genomic hybridization (CGH) constitutes a powerful tool for identification and characterization of bacterial strains. In this study we have applied this technique for the characterization of a number of Lactobacillus strains isolated from the intestinal content of rats fed with a diet supplemented with sorbitol. Phylogenetic analysis based on 16S rRNA gene, recA, pheS, pyrG and tuf sequences identified five bacterial strains isolated from the intestinal content of rats as belonging to the recently described Lactobacillus taiwanensis species. DNA-DNA hybridization experiments confirmed that these five strains are distinct but closely related to Lactobacillus johnsonii and Lactobacillus gasseri. A whole genome DNA microarray designed for the probiotic L. johnsonii strain NCC533 was used for CGH analysis of L. johnsonii ATCC 33200T, L. johnsonii BL261, L. gasseri ATCC 33323T and L. taiwanensis BL263. In these experiments, the fluorescence ratio distributions obtained with L. taiwanensis and L. gasseri showed characteristic inter-species profiles. The percentage of conserved L. johnsonii NCC533 genes was about 83% in the L. johnsonii strains comparisons and decreased to 51% and 47% for L. taiwanensis and L. gasseri, respectively. These results confirmed the separate status of L. taiwanensis from L. johnsonii at the level of species, and also that L. taiwanensis is closer to L. johnsonii than L. gasseri is to L. johnsonii. Conventional taxonomic analyses and microarray-based CGH analysis have been used for the identification and characterization of the newly species L. taiwanensis. The microarray-based CGH technology has been shown as a remarkable tool for the identification and fine discrimination between phylogenetically close species, and additionally provided insight into the adaptation of the strain L. taiwanensis BL263 to its ecological niche.
( 2009 )
Lactobacillus taiwanensis sp. nov., isolated from silage.
PMID : 19605711 : DOI : 10.1099/ijs.0.006783-0
Strain FIRDI 006T, isolated from silage cattle feed, was characterized by using phenotypic and molecular taxonomic methods. The strain was a homofermentative lactic acid bacterium; the cells stained Gram-positive and were catalase-negative, non-motile, facultatively anaerobic rods. 16S rRNA gene sequence analysis revealed that the strain belongs phylogenetically to the genus Lactobacillus and can be placed within the Lactobacillus acidophilus-delbrueckii group. Lactobacillus gasseri and Lactobacillus johnsonii were the most closely related species, with 16S rRNA gene sequence similarities of 99.53 and 99.46% to the respective type strains. Low gyrB gene sequence similarities (<90%) and low DNA-DNA reassociation values (<45%) were obtained between the strain and the phylogenetically closest neighbours. Based on phenotypic and genetic evidence, the strain is considered to represent a novel species, for which the name Lactobacillus taiwanensis sp. nov. is proposed. The type strain is FIRDI 006T (=BCRC 17755T =DSM 21401T).
( 2012 )
Discrimination of the Lactobacillus acidophilus group using sequencing, species-specific PCR and SNaPshot mini-sequencing technology based on the recA gene.
PMID : 22555934 : DOI : 10.1002/jsfa.5692
To clearly identify specific species and subspecies of the Lactobacillus acidophilus group using phenotypic and genotypic (16S rDNA sequence analysis) techniques alone is difficult. The aim of this study was to use the recA gene for species discrimination in the L. acidophilus group, as well as to develop a species-specific primer and single nucleotide polymorphism primer based on the recA gene sequence for species and subspecies identification. The average sequence similarity for the recA gene among type strains was 80.0%, and most members of the L. acidophilus group could be clearly distinguished. The species-specific primer was designed according to the recA gene sequencing, which was employed for polymerase chain reaction with the template DNA of Lactobacillus strains. A single 231-bp species-specific band was found only in L. delbrueckii. A SNaPshot mini-sequencing assay using recA as a target gene was also developed. The specificity of the mini-sequencing assay was evaluated using 31 strains of L. delbrueckii species and was able to unambiguously discriminate strains belonging to the subspecies L. delbrueckii subsp. bulgaricus. The phylogenetic relationships of most strains in the L. acidophilus group can be resolved using recA gene sequencing, and a novel method to identify the species and subspecies of the L. delbrueckii and L. delbrueckii subsp. bulgaricus was developed by species-specific polymerase chain reaction combined with SNaPshot mini-sequencing.
( 2013 )
Lactobacillus pasteurii sp. nov. and Lactobacillus hominis sp. nov.
PMID : 22328611 : DOI : 10.1099/ijs.0.036665-0
Strains 1517(T) and 61D(T) were characterized by phenotypic and molecular taxonomic methods. These Gram-positive lactic acid bacteria were homo-fermentative, facultatively anaerobic short rods. They were phylogenetically related to the genus Lactobacillus according to 16S rRNA gene sequence analysis, with 99 % similarity between strain 1517(T) and the type strain of Lactobacillus gigeriorum, and 98.6, 98.5 and 98.4 % between strain 61D(T) and Lactobacillus gasseri, Lactobacillus taiwanensis and Lactobacillus johnsonii, respectively. Multilocus sequence analysis and metabolic analysis of both strains showed variation between the two strains and their close relatives, with variation in the position of the pheS and rpoA genes. The DNA-DNA relatedness of 43.5 % between strain 1517(T) and L. gigeriorum, and 38.6, 29.9 and 39.7 % between strain 61D(T) and L. johnsonii, L. taiwanensis and L. gasseri, respectively, confirmed their status as novel species. Based on phenotypic and genotypic characteristics, two novel species of Lactobacillus are proposed: Lactobacillus pasteurii sp. nov., with 1517(T) (= CRBIP 24.76(T) = DSM 23907(T)) as the type strain, and Lactobacillus hominis sp. nov., with 61D(T) (=CRBIP 24.179(T) = DSM 23910(T)) as the type strain.